Formerly the general manager at AOL Media Networks, Lebow had split his time between the East Coast and IB headquarters in St. Paul, Minn. The lengthy commute was a factor in his departure, said an IB spokesperson.

IB handles the Websites for several blue-chip station groups, including Hearst, McGraw-Hill and Post-Newsweek, all of whom have equity in IB. But rivals such as WorldNow, Inergize Digital and Broadcast Interactive Media have gained ground.

The IB spokesperson said CFO Steve Johansen will oversee day-to-day operations during the CEO search, and that IB's "strategic direction will stay the same."

Lebow issued an internal memo May 12 that reads: "IB has many opportunities ahead with broadcasters and advertisers again looking to invest and grow. Having completed this chapter at IB, it is now the right time for me to step back and consider other personal and career objectives that I have set."

Lebow says his contract with IB was up and he may look at entrepreneurial opportunities in New York's Silicon Alley online space.